email.message_from_binary_file creates invalid RFC2047 encodings

Bug report

Bug description:

The following illustrates the issue.

>>> # Here's an example file
>>> with open('badx2.eml') as fp:
...     print(fp.read())
...     
From: "Sweepstakes Alert–Dyson Vacuum" <DysonVacuumSweeps@stellaryx.space>

body

>>> # Note that the `–` above is a unicode En Dash
>>> # Make a message object
>>> from email import message_from_binary_file
>>> with open('badx2.eml', 'rb') as fp:
...     msg = message_from_binary_file(fp)
...     
>>> # and look at it
>>> print(msg.as_string())
From: =?unknown-8bit?q?=22Sweepstakes_Alert=E2=80=93Dyson_Vacuum=22_=3CDysonVacuumSweeps=40stellaryx=2Espace=3E?=

body

>>> # Note that the email address is improperly included in the encoded word

CPython versions tested on:

3.13

Operating systems tested on:

Linux

まず、email.message_from_binary_file を使って示された例を再現し、email パッケージのヘッダーエンコーディングの処理経路を調査します。表示名がメールアドレスを誤って含めずにエンコードされ、Unicode の en dash のケースをカバーするリグレッションテストがあることをもって完了とします。